As micro-fluid ejection devices become smaller and the frequency of ejection of fluid from ejection heads for the devices becomes greater, the ejection heads have become more susceptible to a variety of occurrences which may lead to misfiring of certain ejection actuators on the ejection heads. One such occurrence is the presence of a gas bubble in a fluid chamber of the ejection head. Because of the small size of the fluid chambers and associated ejection orifices, even minute gas bubbles in the fluid chambers may be effective to block fluid flow from the ejection orifices. There are a number of sources that may lead to the formation of gas bubbles in the fluid chambers. For example, impact of the ejection head on a hard surface may form gas bubbles in the fluid chambers. Another source of gas bubbles may be dissolved air or oxygen in the fluid.
In order to reduce the occurrence of gas bubbles in the fluid chambers, impact of the ejection head may be minimized. Another method for reducing the occurrence of gas bubbles may be to provide an ejection head design which is less susceptible to retaining gas bubbles in the fluid chambers. However, neither of these solutions is completely satisfactory. Accordingly, there remains a need for an improved system and method for purging bubbles from a micro-fluid ejection head.
With regard to the foregoing, the disclosure provides in one exemplary embodiment a method for purging bubbles from a fluid chamber of a micro-fluid ejection head containing a plurality of fluid chambers, an ejection actuator respectively associated with each of the fluid chambers, and a common fluid supply area for the fluid chambers. According to this exemplary method, one or more of the ejection actuators are pulsed with energy sufficient to expand a bubble present in one of the fluid chambers without substantially boiling the fluid in the common fluid supply area. A first temperature of the ejection head is maintained for a first period of time during bubble expansion so that the bubble in the fluid chamber is urged away from the fluid chamber in the absence of applying a pressure to the fluid chamber. The ejection head temperature is decreased over a second period of time to lower the ejection head temperature to a second temperature lower then the first temperature.
In another exemplary embodiment, there is provided a micro-fluid ejection device including a micro-fluid ejection head containing a plurality of fluid chambers, fluid actuator devices associated with the fluid chambers, a fluid supply inlet, and fluid supply channels in fluid flow communication with the fluid supply inlet and each of the fluid chambers. A fluid supply reservoir is in fluid flow communication with the fluid supply inlet. The ejection actuators are capable of being pulsed with an energy sufficient to expand any bubbles present in the fluid chambers, without substantially boiling the fluid in the fluid supply inlet, and to force the bubbles present in the fluid chambers away from the fluid chambers.
An advantage of the exemplary embodiments can be that boiling the fluid in a common fluid supply area of the ejection head is substantially avoided. Furthermore, the system can use existing ejection actuators without the need for additional ejection head heaters to effect a temperature rise of the ejection head. Since individual ejection actuators can be used for the bubble purging procedure, heat may be directed specifically to chambers containing bubbles thereby enabling lower ejection head temperatures to be used to effectuate removal of the bubbles. Specific elements of the bubble purging procedure can enable bubbles to be purged and/or shrunk to the point where they disappear from the fluid chamber.